Mercurial > dropbear
diff libtommath/bn_mp_mul_d.c @ 389:5ff8218bcee9
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 2af95f00ebd5bb7a28b3817db1218442c935388e)
to branch 'au.asn.ucc.matt.dropbear' (head ecd779509ef23a8cdf64888904fc9b31d78aa933)
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Thu, 11 Jan 2007 03:14:55 +0000 |
parents | eed26cff980b |
children | 60fc6476e044 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/libtommath/bn_mp_mul_d.c Thu Jan 11 03:14:55 2007 +0000 @@ -0,0 +1,79 @@ +#include <tommath.h> +#ifdef BN_MP_MUL_D_C +/* LibTomMath, multiple-precision integer library -- Tom St Denis + * + * LibTomMath is a library that provides multiple-precision + * integer arithmetic as well as number theoretic functionality. + * + * The library was designed directly after the MPI library by + * Michael Fromberger but has been written from scratch with + * additional optimizations in place. + * + * The library is free for all purposes without any express + * guarantee it works. + * + * Tom St Denis, [email protected], http://math.libtomcrypt.com + */ + +/* multiply by a digit */ +int +mp_mul_d (mp_int * a, mp_digit b, mp_int * c) +{ + mp_digit u, *tmpa, *tmpc; + mp_word r; + int ix, res, olduse; + + /* make sure c is big enough to hold a*b */ + if (c->alloc < a->used + 1) { + if ((res = mp_grow (c, a->used + 1)) != MP_OKAY) { + return res; + } + } + + /* get the original destinations used count */ + olduse = c->used; + + /* set the sign */ + c->sign = a->sign; + + /* alias for a->dp [source] */ + tmpa = a->dp; + + /* alias for c->dp [dest] */ + tmpc = c->dp; + + /* zero carry */ + u = 0; + + /* compute columns */ + for (ix = 0; ix < a->used; ix++) { + /* compute product and carry sum for this term */ + r = ((mp_word) u) + ((mp_word)*tmpa++) * ((mp_word)b); + + /* mask off higher bits to get a single digit */ + *tmpc++ = (mp_digit) (r & ((mp_word) MP_MASK)); + + /* send carry into next iteration */ + u = (mp_digit) (r >> ((mp_word) DIGIT_BIT)); + } + + /* store final carry [if any] and increment ix offset */ + *tmpc++ = u; + ++ix; + + /* now zero digits above the top */ + while (ix++ < olduse) { + *tmpc++ = 0; + } + + /* set used count */ + c->used = a->used + 1; + mp_clamp(c); + + return MP_OKAY; +} +#endif + +/* $Source: /cvs/libtom/libtommath/bn_mp_mul_d.c,v $ */ +/* $Revision: 1.3 $ */ +/* $Date: 2006/03/31 14:18:44 $ */